Lookups on known set of integer keys

Question

Gperf consistently underperforms a Judy array in my environment, and I\'m wondering if there is another perfect hash library out there built specifically for integer keys. I

Answer 1

Keep your keys sorted, and use an M-tree to retrieve any key.

An M-tree has M entry per node, instead of 2 for binaries. It will help tremendously for performance. Use a cache line size as the basis of your node size, hence 64 Bytes. You can store 16 32bits values in this size.

Since you have 1000 values, 3 levels will be enough to retrieve the right key (as opposed to 10 levels for a binary tree).

Another idea would be to hash your keys into a small hash-table, such as 12-bits one (4K entries), and solve the potential collisions with a simple chain. You are very likely to get most of your keys in a single search.